The present invention relates to an output voltage detecting device in a laser oscillator, and more particularly to an output voltage detecting device in a laser oscillator, in which an output voltage can be detected with a circuit having a simple configuration.
A laser tube for use in a gas laser device has an electrical impedance which varies depending upon an interiorly confined gas status. As a consequence, a voltage supplied to the laser tube varies. For example, in a laser oscillator having a current feedback loop with which a current is fedback to the laser tube, the variation in the electrical impedance of the laser tube causes the supply voltage to vary since the current is being controlled to be constant. If this condition remains semiconductor elements, the laser tube or other elements forming an inverter are damaged.
In view of the foregoing, it is a conventional practice to detect the voltage supplied to the laser tube. When the resultant voltage is above a reference voltage, an alarm is generated. When the detected voltage is above a danger-level voltage, the driving is stopped. In addition, it has been necessary to detect and monitor the output voltage in order to control the output voltage to be constant.
However, when a transformer is used, it is required to have a considerably high voltage insulation resistivity. The transformer is further required to have a high frequency characteristic attendant to the high frequency power supply unit. For such reasons, the transformers which are extremely expensive have to be employed.
A method in which the voltage is divided by capacitors has a problem in that a power supply line led to the laser tube cannot be isolated from a ground connection of a control apparatus, so that noise is liable to be introduced into a control circuit.